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e _ " -tom j ��-reti- _ -asr'a '"-.cgl -- �, a a.. .I According to the San Joaquin County Flood Control and Water '.� Conservation District, Spring 1990, the regional groundwater gradient is to the east - northeast. The nearest surface water body to the site is the Stockton Deep Water Channel which trends east to west and is connected to the Sacramento F - San Joaquin Delta. The east end of the channel terminates just west of the site at Center Street. The site itself overlies the former east end of the channel. The site is also located. approximately 2.75 miles south of the Calaveras River and 2.5 miles north of Walker Slough, a tributary of the San Joaquin River. r A survey of all water wells within a one-mile radius of the site was conducted based on information received from the California Department of Water Resources. The closest well to the site in due east of the site on El Dorado Street. The approximate locations of known water wells within a one-wile radius of the site are plotted on Figure 3. "f 3.1 Site Specific Hydrogeologic Setting P;-evious investigations at the facility show that soils beneath much of the site Consist primarily of clays (CL/CH) from surface to approximately 26 feet below grade with a zone of elastic silt (mm) ,. and clay (CL) to a depth of 36 feet, the maximum depth of the unsaturated zone. However, in the central portion of the site, IF roughly coincident with the area` of the former tank excavwLion, the site is comprised largely of cards. A portion of this material may V be fill from offsite, placed- in .the excavation to a depth of approximately 12 feet below grade. From skj?proximately 12 to 26 feet below grade, the native material is largely sand as indicated by the } logs from borings SB3, SH4, SB9, VP1 and VP2 (Appendix 1) . Current depth to groundwater at the site is approximately 35 feet below grade. Groundwater gradient at the site is toward the north - northeast at 0.005 feet per feet or 26 feet per mile (Figure 4) . weber Palet Property - 475 "' aUPOyfl.ilY - .